300W USB 12v Invertor

Dec 31, 2010
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I have a 300W USB 12v Invertor that, according to the box, features
DC 5v 500ma (max) Usb charging socket for devices such as mobile phone chargers, sat navs and mp3 players.
It also has a 3 pin plug socket that would allow me to plug in my mains charging unit for my laptop.
The technical information on the box includes
Output voltage AV 230V +/- 5%
Output Frequency 50 Hz
Output power 300w continuous
Peak output power 900w maximum
Output waveform modified sine wave

As I have read somewhere (Think it was to with generators though) that a wrong sine wave can nadger computers I am wondering if I can charge my laptop with this invertor, can some wise boffin tell me please?

Norman
 
Apr 27, 2008
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You can, though some think that a pure sine wave inverter is safer. Laptop power supplies output DC usually 18-20v, and there is a theory that the sawtooth waveform of the non pure sine wave ones may produce AC 'noise' on the output.
My personal view is that it's best to use a 12v DC to DC power supply for a laptop. There are 'universal' ones which you have to set the voltage/fiddle about with interchangeable plug tips or you can buy one specially for your laptop, as I have for my Dell.
 
Sep 23, 2013
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Unfortunately. the answer is - 'It all depends...'

If the laptop is reasonably new, then it should be fine. My understanding (he said, covering his a*se) is that laptops that have switched mode power supplies are fine. One clue is to look at the rated input voltage on your charger. If it says something like 110 - 240V, then as far as I know, it is switched mode & should also be fine with a modified sine wave inverter.

I also believe that there is more than one version of modified sine wave. The difference being how big the steps in the wave form are - the smaller the step, the closer to a true sine wave it is. But that is rarely quoted on the box.

Mine hasn't blown up yet! :)
 
Sep 23, 2013
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If you didn't have an inverter already & if you didn't have any other use for one other than charging the laptop, then I would say go for a DC to DC converter & eliminate the risk. Probably more efficient as well.
 

pappajohn

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Aug 26, 2007
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One problem with inverters and phone/laptop chargers etc......

You start with 12vdc, then invert it to 230vac with maybe 10% efficiency loss, then reduce it back to 12v/18vdc via the phone/laptop charger, again with efficiency losses.

The losses add up to wasted amps.

A 12v to 12v/18v charger there is very little efficiency loss and a correctly regulated voltage.
 
Sep 16, 2010
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Are we OK plugging a 300 watt inverter into the Cig lighter socket in the back that comes off the hab batts via the Sargent 500 ??? Please..
 

pappajohn

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Are we OK plugging a 300 watt inverter into the Cig lighter socket in the back that comes off the hab batts via the Sargent 500 ??? Please..
If you use the inverter at its full 300watt potential then no, it will draw 25amps at 300watts and you cig lighter socket will be fused at 10 or 15 amps
 
Sep 23, 2013
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Better to wire it directly to the batteries if you can & miss out the socket altogether. Many would also suggest fitting it's own in-line fuse unless the inverter is close to the batteries (it should be as close as you can get it anyway).

Are you saying that the inverter was supplied ready wired with a cigarette lighter plug? That sounds unusual for a 300W inverter. It would be very unusual to find a 12V socket that was either fused or wired to carry the current that would draw on full power.
 

Welsh girl

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Nov 7, 2009
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We bought a 300w sine wave inverter that came with 2 sets of cables. One to be used with a cigarette lighter socket and one with crocodile clips.
We have since wired it permanently I the battery with an inline fuse.
I know it can't be used to its full potential with the cigarette socket though as it should be a 10 amp.
 

Lindacarole

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Mar 23, 2014
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Now a year !
https://www.e-bikeshop.co.uk/.../bosch-ebike-12v-travel-battery-car-char.

Just seen this excuse my ignorance but would this Bosch charger work with other batteries? I am purchasing a Kalkhoff bike and wondered it this would work.
thanks
Linda
 
Jul 29, 2012
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Not long enough, but a little common sense helps..........
Linda, I have 2 x eBikes and use the charger via our 2000watts inverter without problem. When parked up they can draw 8amps per hour so can/will drain your battery quickly, but we tend to charge whilst on the move. A 300W USB 12v Invertor ( pure S/wave ) will do the job for you.
 

Lenny HB

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https://www.e-bikeshop.co.uk/.../bosch-ebike-12v-travel-battery-car-char.

Just seen this excuse my ignorance but would this Bosch charger work with other batteries? I am purchasing a Kalkhoff bike and wondered it this would work.
thanks
Linda
Very unlikely, e-bike batteries & chargers are quite sophisticated kit and very unlikely one manufacturers charger would work with another's batteries, at 150 quid expensive to find out with a risk of damaging a £600 battery, also you would need to source the correct plugs for the batteries. The Bosch 12v charger is lower power than the mains one and takes 5 hours to charge a 400-watt battery compared to 2½ for the mains charger.

Like John, I fitted an inverter in my case a 1000-watt pure sine wave.
 

Lindacarole

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Mar 23, 2014
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Thanks John and Lenny now looking at inverters as the way to go. Will take your advice and charge it on the move.
Regards
Linds
 
Jul 29, 2012
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Not long enough, but a little common sense helps..........
Very unlikely, e-bike batteries & chargers are quite sophisticated kit and very unlikely one manufacturers charger would work with another's batteries, at 150 quid expensive to find out with a risk of damaging a £600 battery, also you would need to source the correct plugs for the batteries. The Bosch 12v charger is lower power than the mains one and takes 5 hours to charge a 400-watt battery compared to 2½ for the mains charger.

Like John, I fitted an inverter in my case a 1000-watt pure sine wave.
Pure sine wave is the way to go, however modified sine wave may also work, but I would contact the eBike maker and check. I sure someone will come up and add their thoughts.
 
Aug 6, 2013
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Pretty well all chargers for all applications are now switched mode. These work by rectifying the incoming AC and using the resultant output to either operate a small inverter whose output is rectified or by using the rectified incoming AC to produce the output directly. The output is pulsed with a variable on/off ratio and smoothed to reduce it to the required charging voltage. No remnant of the incoming waveform can survive that lot meaning that 'modified sine wave' is safe to use. Clear as mud :xgrin:.
 
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